This invention relates generally to strapdown inertial navigation systems and more specifically to attitude updating and coning algorithms which reduce system drift errors in the presence of coning motion.
One of the key parameters of a strapdown inertial navigation system is its response to coning motion. Substantial efforts have gone into the development of sophisticated coning algorithms which reduce system drift errors in the presence of coning motion. Present-day algorithms typically use incremental angle outputs from the gyros to form high order correction terms which reduce net coning errors (J. Mark, D. Tazartes, et. al., "Extension of Strapdown Attitude Algorithm for High-Frequency Base Motion", Journal of Guidance, Control, and Dynamics, Vol. 13, No. 4, July-August 1990). These algorithms assume a flat transfer function for the processing of the incremental angle outputs and are structured to yield very high order responses.
Techniques such as gyro resolution enhancement as described in U.S. Pat. No. 5,485,273, which is hereby incorporated by reference, (also described in J. Mark & D. Tazartes, "A Resolution Enhancement Technique for Laser Gyros", Proceedings of Fourth St. Petersburg International Conference on Integrated Navigation Systems, St. Petersburg, Russia, May 1997) can provide high resolution angle data. However, the gyro data processed for resolution enhancement has a "shaped" frequency response which must be accounted for in the design of coning algorithms.
While resolution enhanced data has been used for angular rate outputs, it has not been used in attitude generation although it would be very beneficial for applications requiring low noise, high resolution attitude information.